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impact on Earth’s atmosphere

...interior and from the metabolic activities of life-forms—as opposed to the primordial atmosphere, which developed by outgassing (venting) during the original formation of the planet. Current
volcanic gaseous emissions include water vapour (H
2O), carbon dioxide (CO
2), sulfur dioxide (SO
2), hydrogen sulfide (H
2S), carbon monoxide (CO), chlorine...

role in volcanism

...of explosive destruction, the hot, ash-laden gas clouds associated with an explosive eruption can scorch vegetation and kill animals and people by suffocation. Gas clouds emitted from fumaroles (
volcanic gas vents) or from the sudden overturn of a crater lake may contain suffocating or poisonous gases such as carbon dioxide, carbon monoxide, hydrogen sulfide, and sulfur dioxide. At Lake...